The invention relates to a disassemblable ball and socket joint, useful particularly for connecting a compressed gas spring to a support element.
In motor vehicles, the compressed gas springs used to balance the movable shutters such as hood, trunk or tailgate door are connected most frequently to the vehicle body by means of ball and socket joints. This joint generally consists of two parts: a steel ball integral with the body and with the shutter, and a plastic or metal cage integral with the compressed gas spring.
The compressed gas springs are frequently fitted in the gutters located on each side of the tailgate; they are exposed to bad weather, and hence to corrosion, particularly at the base of the cage which is fitted on the end of the tube, because water may be retained in that region.
On the other hand, production efficiency dictates a wish to use joints which can be fitted extremely rapidly, preferably in a single operation, this comprising both the positioning of the cage on the ball and the placing of the locking means in the active position. This excludes joints of the old type, where it is necessary to work in two stages: first of all place the ring on the ball by a movement parallel to the axis of the journal which carries the ball, then move the locking means in a different direction, by sliding them perpendicular to the journal for example.
GB No. A-323,976 patent to Bolton describes a ball and socket joint of a different type. Like the others, this ball and socket joint comprises on the one hand a spherical ball integral with a journal, and on the other hand a cage having a cavity adapted to receive the ball substantially without play and connected to the exterior by a cylindrical channel of the same diameter, said cage being further provided with fixing means to a support. The special feature of the joint of this patent is that it is provided with a generally C-shaped resilient ring, the body of which surrounds said cage, passing beyond the base of the cavity, and the ends of which enter two slots of the cage arranged on either side of the channel, of constant width and leading into the channel to permit the ends of the ring to project inside the channel and to retain the ball in the cavity, said slots being oblique relative to the axis of the channel and receding from the center of the cavity in approaching said axis. It follows from this arrangement that a force tending to remove the ball from its housing produces a wedging effect of the ends of the ring in their slots, which effectively resists the exit of the ball.
The above-mentioned GB No. A-323,976 provides for the use, for the purpose of assembly, of a small tongue-shaped tool supplied with the cage and placed between the outside of the latter and the ring, near the outer end of a slot. By pivoting this tool, the end of the ring is moved away from the axis of the channel. The assembly therefore comprises three operations: retracting the ends of the ring, introducing the ball into the cage, releasing the ring. However, it is conceivable that, by a judicious choice of the shape and of the angle of the ends of the ring, the latter might be separated by the ball itself, so that the assembly would be performed in a single operation. However, the tongue-shaped tool would still remain necessary for the dis-assembly, and there would be a risk of finding this dis-assembly impossible if, due to insufficient lateral accessibility, it were possible to effect the positioning by a simple relative movement of the cage and of the ball without being able to activate the tool afterwards. The device of this document also presents a corrosion risk at the point where the ring is constantly in contact with the ball, because wear removes the protection at the contact position.
The modifications which have to be made to the cage of the device of GB No. A-323,976 in order to permit assembly in a single operation evidently present a multiplicity of problems. If the angle formed by the ends of the ring with the axis of the channel approaches a right angle, according to the mutual separation of said ends, it is possible to have either easy assembly but lack of effective locking, or else impossibility of assembly, or risk of straining the ring, but highly effective locking. If the shape of the ring approaches that of an arc of a circle, it is in danger of turning on itself during transport or during handling prior to assembly, and obstructing the channel, which renders the assembly impossible.
The same inconvenient result may occur at the time of assembly if, due to an irregularity, the ball pushes one of the ends of the ring without being in contact with the other; this then causes the ring to rotate upon itself. It should also be observed that, very frequently, the balls exhibit a flat at their summit in order to permit fixing of the journal to a support by riveting. As a result of this, the tolerances on the position of the ends of the ring are close. It therefore appears necessary to anchor the ring firmly relative to the cage in order to prevent it rotating.
Another disadvantage of ring shapes too close to that of an arc of a circle is that they compel the provision of wide slots, particularly on the side of their outer end, in order to permit easy positioning of the ring. Excessively wide slots reduce the mechanical strength of the cage. On the other hand, extremely narrow slots, although they may facilitate the solution of the problem of rotation of the ring, are difficult to obtain.